Studies have shown there is a relation between the occurrence of complications in diabetes mellitus patients and the amount of native fluorescence, or autofluorescence, of the eye lens and of skin biopsies. Reference is made to, for instance, Sell, D. R. et al., Pentosidine formation in skin correlates with severity of complications in individuals with long-standing IDDM, Diabetes 1992; 41:1286-92.
According to the current insights, this relation is attributed to the presence of so-called AGE's (advanced glycation/glycosylation end products), such as pentosidine. In patients with diabetes mellitus, the AGE level in the skin proves to correlate accurately with preclinical nephropathy and early retinopathy. AGE's are substances originating from irreversible glycoxidation reactions of glucose with amino acid groups of proteins. An example is the pentosidine referred to, which consists of a crosslink between lysine and arginine. The formation of irreversible glycation products on proteins may interfere with the function of such proteins. Formation of AGE's on the collagen of the vascular wall may lead to structural changes, such as less elastic blood vessels. Especially for long-lived structural proteins, such as collagen and elastin, it is of importance that the formation of AGE's proceeds slowly.
The AGE level increases with age, but in healthy people this increase is considerably smaller than in patients with diabetes mellitus.
A method as set forth in the introductory part of claim 1 is known from Marek, H. et al, Increased Collagen-Linked Fluorescence in Skin of Young Patients With Type I Diabetes Mellitus, Diabetes 1990; 5:468-472. In it, the autofluorescence value is determined ex vivo by exciting suspension preparations obtained from material of a skin tissue biopsy. By measuring the native fluorescence of that skin material, the AGE level in a person to be examined can, at least supposedly so, be determined, and it is possible to make predictions about the chances of complications in diabetes.
In this known method, by incision with local anesthesia, a biopsy of clinically normal skin of the buttock is taken. The biopsies are deep-frozen until they are analyzed. Prior to analysis, the skin samples are defrosted and subcutaneous fat is scraped off the skin samples. The residual tissue is washed in a 0.15 M saline solution, dried with filter paper and weighed. Thereafter, selected samples are subjected to homogenization, washing and lipid extraction. The autofluorescence of a thus obtained suspension of the tissue material is measured. For that matter, it has also been previously described that AGE levels in the tissue material of skin biopsies can be determined in ways other than by measurement of autofluorescence.
Drawbacks of this method of determining autofluorescence are that it is necessary to take biopsies from the skin of a patient, that the processing of the skin material for measuring autofluorescence is laborious and time consuming, and that a long period of time elapses between the time when a biopsy is taken and the time when the measuring results become available, so that these results cannot be communicated directly to the patient, which necessitates separate communication to that effect.
The object of the invention is to provide a solution which enables the autofluorescence of skin tissue of patients to be measured in a simpler manner, whereby nonetheless a sufficiently reliable measuring result is obtained.